Difference between old periodic table and new periodic table

The periodic table has undergone several changes and revisions since its inception in the late 19th century. Here are some of the key differences between the old periodic table and the new periodic table:

Old Periodic Table (1869-1913)

• Developed by Dmitri Mendeleev and Julius Lothar Meyer
• Organized elements by their atomic weights and chemical properties
• Had gaps and irregularities, with some elements not fitting neatly into the table
• Did not include isotopes, which were not yet discovered
• Did not have a clear distinction between metals and nonmetals

New Periodic Table (1913-present)

• Developed by Henry Moseley, who introduced the concept of atomic numbers
• Organized elements by their atomic numbers (number of protons in the nucleus) rather than atomic weights
• Introduced the concept of blocks, which group elements with similar electron configurations
• Included isotopes, which were discovered in the early 20th century
• Had a clear distinction between metals, nonmetals, and metalloids
• Has undergone several revisions and updates, including the addition of new elements and the reorganization of existing ones

Some specific changes include:

• The addition of new elements: The periodic table has grown from 63 elements in 1913 to over 118 elements today.
• The reorganization of the table: The table has been rearranged several times to reflect new discoveries and a better understanding of the relationships between elements.
• The introduction of new categories: The table now includes categories such as lanthanides, actinides, and transition metals, which were not recognized in the old table.
• The use of electron configuration: The new table takes into account the electron configuration of elements, which is a key factor in determining their chemical properties.
• The inclusion of isotopes: The table now includes isotopes, which are atoms of the same element with different numbers of neutrons.

Some of the key features of the modern periodic table include:

• The periodic law: The table is organized according to the periodic law, which states that elements with similar properties recur at regular intervals when elements are arranged in order of their atomic numbers.
• The use of blocks: The table is divided into blocks, which group elements with similar electron configurations.
• The use of groups and periods: The table is also divided into groups and periods, which group elements with similar chemical properties and electron configurations.
• The inclusion of noble gases: The table includes the noble gases, which are a group of elements that are chemically inert and have similar electron configurations.

Overall, the new periodic table is a more accurate and comprehensive representation of the elements and their relationships than the old table. It has been refined over the years through the discovery of new elements and a better understanding of the underlying principles of chemistry.